Been using mine since Saturday and I've had ZERO issues with the back of this case showing finger grease and what not. Either-way, the matte finish TPU wipes clean in no time. I'm a very clean person...but perhaps a burger king board member will have issues in that department?
Also, the frame is a tad more matte finish than the Slim Armors rear cover. No scratches on mine so far. But I think it helps simply due to the fact your not setting the phone down on that plastic like you do with the Slim Armor. The only part that really touches the frame is your hands.
The frame and TPU really feel like a single piece once installed, its pretty awesome how perfect the fit for everything is. Very snug, zero complaints.
In terms of size.... this case is thinner than the Pixelskin HD, which is half the size of the Candyshell already. Going from Candyshell to this will feel like your going caseless almost. It's a slimmer case, but by no means feels cheap on the protection front.
I'll probably be updating my signature below at some point during this week...